How to display particle effect when character hits static mesh in game
You mean with an attack? Or the character just runs into it?
With an attack animation, it is probably best to do some sort of sphere or capsule object trace attached to an anim-notify when you swing the sword/weapon. Then if the trace hits the object type of the mesh, use Spawn System (or Spawn Particle if using Cascace particles) effect nodes.
If you want an effect to spawn whenever the character simply runs into the mesh, have a collision box/capsule/etc. overlap around your character (a second one from the one it starts with). And on overlap event spawn the particle. Again, this will require that it is set to overlap the object type that the mesh is.